Field of the Invention
The present invention relates to a wireless communicator and more in particular to a wireless communicator connectable to different types of wireless communication networks.
Description of the Background Art
In recent years, it has been required to efficiently manage energy used within a local community and a home by spreading management systems known as smart communities, smart houses, smart meters and so on.
For example, a home energy management system (HEMS) and a building energy management system (BEMS) and other systems are proposed to control electric power consumption in a house/building. In the HEMS and the BEMS, the electrical power consumption to be controlled is measured by a distribution board and a smart tap such as an electrical outlet equipped with a communicator in the house/building to collect the values of electrical powers used in the house/building. Furthermore, a smart meter network system is also proposed in which the smart meters automatically measure used amounts of electric power, gas, water and so on, the system receiving the used amounts measured by the smart meters to control the utilities.
IEEE802.15.4, which is established by the Institute of Electrical and Electronics Engineers, Inc., is always available as a standardized specification for the physical layer and the media access control (MAC) layer of wireless communicators constituting a short-distance wireless network. IEEE802.15.4 is a standardized specification in which emphases are placed on costs and power consumption reduction. This standard is appropriate for the above-described wireless networks.
It is required that an apparatus such as a gateway device be connected with various types of networks as well as wireless local area networks (LANs) to receive data and supply the data to servers via the Internet.
In addition, in order to reduce the cost of hardware such as a radio frequency large scale integration (RF-LSI), it is desired that a common data processing circuitry is used for both the physical and the MAC layers. In this case, a gateway device needs to include a plurality of network processors capable of performing processing for a network layer. In the gateway device, a physical (PHY) processor and a MAC processor, which perform processing in lower layers than the network layer, use the common communication channel. It is required that respective network processor use different personal area network identification information (PAN ID).
A MAC processor needs to perform processing while switching the PAN ID according to the network processor that asks for transmission or reception. However, the standardized technique pursuant to IEEE802.15.4 provides no stipulations regarding the method of how to operate the processor when frames having a PAN ID different from the PAN ID set in the MAC processor are received or when frames of a broadcast address are received.
For example, Japanese patent laid-open publication No. 2009-88750 to Saito teaches a management device for managing respective information on a plurality of radio terminals connected to a radio ad hoc network. Furthermore, Japanese patent laid-open publication No. 2009-100327 to Asai teaches a radio network system for quickly detecting the collision of personal area network identification information (PAN ID). However, Saito nor Asai do not provide a solution for the above-mentioned problem.
Where MAC protocol stacks pursuant to IEEE802.15.4 are used, the following problems can arise. Firstly, in the standardized technique of IEEE802.15.4, if frames of a destination PAN ID different from that set in the MAC processor are received, the MAC processor discards the reception frames without transmitting the frames to the network processor. This presents the problem that, if the network processor asks for frame reception, it is necessary for the network processor to urge the MAC processor to modify settings of PAN IDs at some timing. In this respect, if the network processor fails to recognize the timing of the reception frames, then the timing at which the MAC processor is urged to modify the settings of PAN IDs is not obtained. This makes the solution of the problem quite difficult.
Next, upon frame reception, a conventional MAC processor pursuant to IEEE802.15.4 adopts a method of storing the reception frames in a memory and informing a higher-level layer of pointers of the reception frames. However, in this conventional method, if the PAN ID of the reception frames is a broadcast address, then the MAC processor can give a notice of the pointers to only any one of the network processors. This may present the problem that it is impossible to provide a notice to every network processor.
Another possible problem is that, if a MAC processor receives beacon request command frames, then it is not known which network processors should be used in making a reply.